Driving of an instrument or furniture such as, for example, a robot, a hospital bed, a lift chair or the like often requires an actuator that is configured to convert a rotary motion into a reciprocating linear motion. For such an actuator, a reversible electric motor is utilized to generate the rotary motion and a transmission member is coupled to the electric motor so as to convert the rotary motion of the electric motor into the reciprocating linear motion of the actuator. Typically, the electric motor has a rotor. When the electric motor is activated, the rotor rotates along its axis for generating the rotary motion. When the electric motor is deactivated, it is desirable that the rotor would instantly stop from rotating. However, the rotation inertia of the rotor may make it continuously rotate until it firmly stops even the electric motor is deactivated, thereby causing the deviation of the linear motion of the actuator.
In certain applications, the precise control of a linear motion of an actuator is required. This can be achieved by a brake member that is constructed to lock a rotor of an electric motor from rotating when the electric motor is deactivated, and to release the rotor of the electric motor for rotating when the electric motor is activated. There are two types of brakes, a mechanical brake and electromagnetic brake, which are utilized in the conventional actuators. Usually, these brakes are structurally and operably very complicated, and difficult and costly in fabrication. Additionally, the electromagnetic brake, in operation, is much noised.
On the other hand, when the electric motor operates, its rotor is rotating back and forth rapidly, thereby generating heat therein. The generated heat may cause the motor to be malfunctioned or damaged. Therefore, it is desirable for an actuator to have a cooling means for cooling the electric motor in operation.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.